256 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



All of these heavy deposits came from the east (Prince Edward Island) or 

 southeast (New Glasgow, Boston, and Narragansett Basins), and were 

 evidently derived from a notably high and rugged land in these directions. 

 It is probable that they were derived from a distinct range involving the 

 Cobequid Hills, some pre-Pennsylvanian elevations in New Brunswick, 

 and a now-submerged portion which occupied a part of the broad conti- 

 nental shelf which extends as far south as Long Island Sound. Its further 

 extension is entirely problematical. 



The southern basin was evidently much farther removed from any source 

 of coarse sediments. If the range of uplands postulated above was con- 

 tinued any farther south than is indicated by the present contour of the 

 continental shelf, it was separated from the western side of the Appalachia 

 by a continuation of the depression of the northeastern basin in which was 

 trapped the coarse material derived from it, or its trend carried it so far 

 east that only the finer material was transported to the southern basin. 

 It is, perhaps, more probable that the range merged into the generally lower 

 surface of the southern portion of Appalachia and that coarse sediments 

 were not originated in any quantity. 



The general elevation which raised the northern or eastern portion of 

 Appalachia sufficiently to bring it within the possibility of local glaciation 

 and vigorous erosion affected the southern or western portion only sufficiently 

 to initiate a milder erosion under a variable climate resulting in the formation 

 of finer red sediments. 



The progress of the elevation was slow. In the northeastern basin the 

 coarse sediments soon gave place to fine red sands and shales, indicating 

 the lowering of the rugged heights; and in the southern basin the finer red 

 sediments only partially replaced the darker shales, light-colored sandstones, 

 and thin limestones, which shows that the area continued to subside as 

 fast as it was filled. The western part of the southern basin, receiving a 

 far smaller load of deposits, was raised more rapidly until western Kentucky, 

 Indiana, and Illinois were above the plane of deposition; deep valleys were 

 being cut and purely terrestrial beds accumulating while the eastern half 

 was still sinking beneath its increasing burden. The lack of adjacent lands 

 high enough to furnish much sediment under the influence of a variable 

 climate accounts for the lack of red sediments except in small and local 

 patches. North of Ohio and Indiana, the surface of the lower peninsula of 

 Michigan was still covered by coal swamps after sedimentation had ceased 

 to the south. Northern Illinois and Wisconsin were a part of the low-lying 

 land area extending south from the Canadian shield. Similar conditions 

 prevailed to the west, where the highland of Missouri continued to the 

 north through Iowa to the old land of Canada; here Permo-Carboniferous 

 conditions left little trace, for, as has been shown by the author, the red shales 

 and sandstones of Webster County, Iowa, are in all probability a residual 

 soil of Missourian age. 



